Electronic control for heating apparatus

ABSTRACT

A power control device for automatically and proportionately metering power to a heating device used to create a warm microenvironment conducive to the health and growth of an animal during a predetermined incubation period is herein disclosed. The power control device transmits proportionally more power to a heating device where an ambient temperature measured outside of the microenvironment is nearer a predetermined lower limit, and proportionately less power when the ambient room temperature measured outside of the microenvironment is nearer a predetermined upper limit.

FIELD OF THE INVENTION

[0001] This invention relates to an electronic control device forautomatically adjusting the power supplied to one or more heatingdevices so as to maintain a heated microenvironment within the largerenvironment of an animal confinement building.

BACKGROUND OF THE INVENTION

[0002] Infrared heat lamps and/or electric heat mats are often used byswine producers to provide supplemental heat to young and newly bornpiglets. Supplemental heat is required for young piglets because theylack the necessary thermal insulation and the ability to manage theirbody temperature. Without supplemental heat, the piglets would obtainthe necessary warmth from the sow. However, because sows can oftentrample or lay upon piglets, it is desirable to provide the supplementalneeded to warm the piglets using artificial heating devices.

[0003] The supplementary heat is localized to a small area, therebycreating for the piglets a comfortable microenvironment within a largerfarrowing room. Providing localized heat is preferred over large areaheating because of the reduction in energy consumption, improved airquality, and ability to maintain a cooler room temperature, which ismore appropriate for the lactating sows.

[0004] As newborn piglets grow their need for supplemental heat isreduced, allowing for the gradual reduction of supplemental heat duringthe first 2-3 weeks following birth. Various manual and semiautomaticmethods have been devised for reducing this heat, including: raising upthe heat lamps by means of a chain, a rheostat control for manual poweradjustment, on/off thermostats, timers, high/low power switches,unplugging the heat lamp and using circuit breakers or toggle switchesfor manual on/off control. There are also a number of electroniccontrols having variable output power capability that can, to a limiteddegree, and at considerable expense, provide a means to automaticallyadjust the heat output to match the needs of the piglet.

[0005] Thermostats, timers and various other types of on/off switchingdevices lack the ability to modulate the power to the heating device,often resulting in a too hot or too cold condition that causesdiscomfort to the piglet, affecting the health of the animal, and it'sability to efficiently convert feed to weight gain.

[0006] Rheostats and similar manually adjusted devices lack the abilityto dynamically adjust the heater's output in response to changing roomtemperatures and the reduced heat requirement of a growing piglet.Again, this often results in a too little or too much heat being appliedto the microenvironment as the room temperature fluctuates due toseasonal and weather conditions beyond the producer's control. Forexample, a hot summer day can result in a gradual heating of the room tothe extent that supplemental heat is not required for the young piglets.But as the nighttime air cools the room, the need for supplemental heatis again required. Attempting to manually adjust the supplemental heatto match the changing conditions becomes a 24-hour a day managementproblem.

[0007] Some of a current generation of sophisticated electronic controlsdo have the capability of adjusting the output of heating devices basedon temperature and animal age. These controls measure the temperaturewithin the microenvironment near the heating device and regulate theoutput thereof based on a desired microenvironment temperature, using aclosed loop control algorithm. However, from a practical standpoint,these controls are not able to reliably control the large number ofheating devices found in a typical animal confinement building. Thesecontrols have failed to achieve widespread appeal and success due inpart to their high purchase and installation costs. In addition, theskill required to properly setup, operate, maintain, and troubleshootthese complex controls is also a major factor. Other, simpler and lessexpensive controls have sprung up to compete with their relatively morecomplex brethren, but are also limited by their limited capability andhigh installation costs.

[0008] The present invention is therefore directed to the followingobjectives: to provide energy savings through automatic reduction of theheating power applied to heating devices as piglets age; to provideenergy savings through the automatic reduction of heating power appliedto heating devices as the temperature of the farrowing room where thepiglets are kept rises; to obviate the need to manually adjust lampheights or to manually reduce power; to create an improved heatedmicroenvironment for the piglets to result in healthier and moreproductive piglets; to reduce potential for heat stress to the sows byminimizing the heat added to the larger environment of the farrowingroom; to extend the useful life of the heating devices used by providinga soft start feature; to eliminate lamp inrush current so that lamps runcooler at reduced power levels; to reduce peak demand from backupgenerators or power utilities; and, to reduce piglet mortality due tocrushing by maintaining a comfortable microenvironment that allows youngpiglets to keep away from the sow. In addition to its use in farrowingoperations, it is to be understood that the present invention issusceptible of use in agricultural, zoological and home settings withmyriad animals, including but not limited to, birds such as chickens andturkeys, dogs, and cats.

[0009] These and other objectives and advantages of the invention willappear more fully from the following description, made in conjunctionwith the accompanying drawings wherein like reference characters referto the same or similar parts throughout the several views.

SUMMARY OF THE INVENTION

[0010] The objects of the present invention are realized in a method ofcontrolling the heat applied to a microenvironment in such a manner asto promote the health, wellbeing, and growth of a young animal presentwithin the microenvironment. This method begins with the step ofproviding a heating device that is constructed and arranged to createthe heated microenvironment within a larger environment. Next, a lowtemperature limit at and below which the heating device will operate atsubstantially 100% of its rated power is chosen, as is a hightemperature limit at which the heating device will be caused to operateat substantially 0% of its rated power. The temperature of the largerenvironment outside of the microenvironment is then measured and poweris applied the heating device based on this measurement. Where thetemperature of the larger environment is below the high temperaturelimit, the heating device will be activated to create the heatedmicroenvironment. The power that is applied to the heating device isvaried with the temperature of the larger environment so as to maintaina continuous heat output from the heating device. The power applied tothe heating device ranges from 0%-100% of the rated power for theheating device and is applied over that range of temperatures defined bythe upper and lower temperature limits. The power applied to the heatingdevice is set to 100% of rated power when the temperature of the largerenvironment is at or below the lower temperature limit and is set to 0%when the temperature of the larger environment is above the uppertemperature limit.

[0011] Power may be applied to the heating device in a linear ornon-linear manner and may be varied discontinuously or continuously. Ina preferred embodiment of the present invention, power is applied to theheating device so as to obtain a linear output from the heating device.

[0012] A preferred embodiment of a control mechanism for controlling thepower applied to a heating device comprises a data processor that isoperatively coupled to a memory device, to an operator controlinput/output device, and to a temperature sensor for sensing atemperature of larger environment inside which is created the heatedmicroenvironment. The temperature sensor provides control data to themicroprocessor. The control mechanism is also provided with a variablepower switch that is coupled between a power input and a power output.The variable power switch communicates with and is controlled by thedata processor according to the temperature sensed by the temperaturesensor. The power output of the control mechanism is in turn coupled toa heating device whose output creates the heated microenvironment withinthe larger environment. The variable power switch preferably comprises aswitching mechanism that can be one of a rheostat, a triac, or one ormore thyristors.

[0013] The power control mechanism preferably also comprises a faultchecking circuit for determining whether a fault condition is present.This fault checking is coupled to the microprocessor, which isprogrammed to open the variable power switch if a fault condition issensed. The fault checking circuit preferably shares an induction coilwith a low pass filter. The low pass filter acts to preventelectromagnetic noise that can disrupt electronic equipment in the areaadjacent the power control mechanism.

[0014] A power control algorithm, embodied in the appropriate computercoding, is recorded on the memory device. The power control algorithmdefines a high temperature limit above which power to the heating deviceis cut off and a low temperature limit at and below which power appliedto the heating device is set to 100% of the rated power of the heatingdevice. The power control algorithm varies the power applied to theheating device based on the output of the temperature sensor so as tovary the heat output of the heating device, preferably in a continuousmanner.

[0015] The power control algorithm controls the variable power switchthrough the data processor. Power is provided at levels between 0-100%of the rated power of the heating device for temperatures in the largerenvironment defined by the high and low temperature limits. The powercontrol algorithm is constructed and arranged to supply power throughthe variable power switch such that a heat output of the heating deviceis linear over an operational range that is defined by high and lowtemperature limits.

[0016] In one embodiment of the present invention, all of the componentsof the power control mechanism are located together within a single,sealed enclosure. However, in some applications, the present inventionmay distribute the components of the power control to remote locations.In one such embodiment, the data processor, the memory device, theoperator control input/output device, and the temperature sensor arepositioned outside of the microenvironment and remotely from thevariable power switch. In a distributed embodiment of the power controlmechanism, the data processor may be coupled to a plurality of variablepower switches, each of the plurality of variable power switches beingconstructed and arranged to control power output to a heating devicepositioned within a single microenvironment or to multiple heatingdevices in one or more microenvironments.

[0017] The present invention may also be described as a power controlfor metering the power transmitted to a heating device having a ratedpower capacity that is constructed and arranged to create a warmmicroenvironment conducive to the health and growth of an animal. Thepercentage of the rated power capacity applied to the heating device bythe power control is related to an ambient room temperature and the ageof the animal.

[0018] The power control device sets an high and a low limit that arerelated to an ambient temperature outside of the microenvironment. Thepower control transmits proportionately more power to the heating devicewhere the ambient temperature is nearer the lower limit andproportionately less power where the ambient temperature is nearer thehigh limit. These high and low temperature limits may be modified toadjust the output of the heating devices. For example, the power controlmay periodically lower the high and/or low temperature limits over apredetermined elapsed time period. One example of the present inventionlowers the high temperature limit one degree per day for 25 days.

[0019] Although the disclosure hereof is detailed and exact to enablethose skilled in the art to practice the invention, the physicalembodiments herein disclosed merely exemplify the invention, which maybe embodied in other specific structure. While the preferred embodimentshave been described, the details may be changed without departing fromthe invention, which is defined by the claims.

DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a table setting forth the algorithm whereby powersettings are modified to maintain a suitable microenvironment whilesimultaneously reducing power consumption;

[0021]FIG. 2a is a perspective view of the present inventionillustrating a portable embodiment of the present invention having builtin power receptacles;

[0022]FIG. 2b is a perspective view of the present inventionillustrating a portable embodiment of the present invention having anoutput power cord with a receptacle at the end thereof;

[0023]FIG. 3 is a schematic of one embodiment of a circuit that enablesthe present invention;

[0024]FIG. 4 is a schematic view of the power control illustrated inFIGS. 2a and 2 b in use in a farrowing operation;

[0025]FIG. 5 is a schematic view of a distributed power control of thepresent invention;

[0026]FIG. 6 is an exploded perspective view of a master control of thepower control illustrated in FIG. 5;

[0027]FIG. 7 is an exploded perspective view of a slave switch of thepower control illustrated in FIG. 5;

[0028]FIG. 8 is a graph of typical power output in (% of rated power) ofa heating element for a given power input (in volts); and,

[0029]FIG. 9 is a schematic illustration of a distributed power controlsystem of the present invention.

DETAILED DESCRIPTION

[0030] The power control of the present invention may be embodied in astand-alone device such as that pictured in FIGS. 2a and 2 b or in ahard-wired version such as that pictured in FIGS. 6-7. Referring firstto FIGS. 2a, 2 b, and 4, a portable embodiment of the power control 10can be seen to comprise a small watertight enclosure 12 with an inputpower cord 14 having a suitable and standard male or female coupling 16,and an external temperature sensor 22. The portable embodiment of thepower control 10 may further comprise one or more built in receptacles21 that are built into the housing 12 (see FIG. 2a) or an output powercord 18 with one or more standard receptacles 20 (see FIG. 2b). Theinput power cord 14, output power cord 18 (where present), and thetemperature sensor 22 preferably enter the enclosure through liquidtight strain relief connectors 24, though it is to be understood thatany suitable connection mechanism may be utilized.

[0031] Referring next to FIG. 4, the power control 10 may be usedadvantageously in a farrowing operation to promote the health andefficient growth of piglets. Note that though the power control 10 asdescribed herein is used in a farrowing operation, the power control 10may be reconfigured without exceeding the broad scope of the presentinvention to be used in aviaries, zoos, or in the home for the care ofhousehold pets. The power controls 10 of the present invention aresituated within a farrowing room 40. Within the farrowing room 40 thereare placed one or more farrowing crates 42 in which are confined thesows (not shown). The farrowing crates 42 are provided with mechanismsfor cleaning and feeding the sow and typically have sides that allow thepiglets (not shown) to move freely from the farrowing crate 42 to aheated microenvironment 44. Note that the microenvironment 44 isimmediately adjacent to the farrowing crate 42 and is accessible to thepiglets. Note also that the farrowing crate 42 and the microenvironmentare fenced to prevent the piglets from escaping to the largerenvironment of the farrowing room 40 in general.

[0032] While FIG. 4 illustrates only two farrowing crates 42,microenvironments 44, and associated power controls 10, it is to beunderstood that a farrowing room 40 may contain any number of farrowingcrates 42. In addition, while FIG. 4 illustrates only a single heatingdevice 30 in use with each of the respective power controls 10, it is tobe understood that a single power control 10 may be used to controlmultiple heating devices 30.

[0033] Heating devices 30 are arranged with respect to themicroenvironments 44 so as to provide heat thereto. While the heatingdevices pictured in FIGS. 4 and 5 are schematic illustrations ofinfrared lamps of one type or another, it is to be understood that thepower controls 10 of the present invention may be readily adapted foruse with virtually any electrically powered heating device, includingbut not limited to, heat lamps and heating pads. In addition, with theprovision of a suitable control valve (not shown), the power controls 10could be adapted to operate gas or oil fired heating devices (notshown).

[0034] A heating device 30 is installed in its predetermined position inor adjacent the microenvironment 44 such that heat energy 36 is directedinto the microenvironment 44. Where the heating device 30 is a lamp,heat energy 36 will be radiated into the microenvironment 44 viainfrared radiation. Where the heating device 30 is a heat mat, the heatenergy 36 is generally transmitted into the microenvironment 44 bythermal conduction. Installation of the embodiments of the power control10 shown in FIGS. 2-4 comprises plugging a heating device 30 into thepower control 10 output receptacle 20 or 21 as the case may be. Thepower control 10 power cord 14 is then connected using plug 16 to astandard electrical outlet (not shown). While the enclosure 12 of thepower control 10 may simply rest on the floor of the farrowing room 40,it is preferred to hang or mount the enclosure 12 off the floor to avoiddamage thereto. The power control 10 may be provided with elongate powercords 14, 18 of a length that would allow for the mounting of theenclosure 12 in a desired location. As the power control 10 operates onan open loop basis, the temperature sensor 22 must be mounted outside ofthe microenvironment 44 and otherwise away from the heating devices 30.The temperature sensed by the sensor 22 will accordingly be thetemperature of the larger environment of the farrowing room 40 ratherthan that of the microenvironment(s) 44. In general, as the temperatureof the farrowing room 40 goes up, the power applied to the heatingdevices 30 is reduced and vice versa.

[0035] The power control 10 modifies the output of the heating devices30 by modulating the input power (voltage) to the heating devices 30over an adjustable range of between 0% and 100%. The power input rangeis determined by the rated power output of the power control 10. Wherethe power control 10 is rated at a maximum output of 120 volts, theadjustable range of power input to the heating device will vary between0 volts (0%) to 120 volts (100%). Similarly, where the power control 10is rated for a maximum output of 240 volts, the adjustable range ofpower input to the heating device will vary between 0 volts (0%) to 240volts (100%). Note that the power control may be adapted to control anysuitable power range, this range typically being determined by thenature of the heating devices 30 themselves as heating devices 30 ratedat 120 volts will require a power control rated at 120 volts and heatingdevices rated at 240 volts will require a power control rated at 240volts. The power input to the heating devices 30 is managed bycorrelating the measured room temperature outside of themicroenvironment 44 and the time elapsed since the heating device 30 wasactivated to create the heated microenvironment 44.

[0036] The power control band is based on a LOW temperature settingcorresponding to the desired temperature for minimum heat output (0%power) and a HIGH temperature setting corresponding to the desiredtemperature for maximum heat output (100% power). When the measured roomtemperature is between the HIGH and LOW settings, the power output tothe heating devices 30 will be modulated to proportionate with respectto the temperature and where it falls on the control band.

[0037] In one preferred embodiment, the power output to the heat devices30 by the power control 10 may be modulated as shown in FIG. 1. In thisembodiment the control band is set to a HIGH limit of 90° F. and a LOWlimit of 70° F. such that where the temperature of the farrowing room 40as determined by temperature sensor 22 is 90° F., the power output tothe heating device 30 will be set at 0%. Similarly, where thetemperature of the farrowing room 40 as determined by temperature sensor22 is 70° F., the power output to the heating device 30 will be set at100%. In general, where the temperature of the farrowing room 40 isbelow the LOW temperature limit, the power output to the heating devices30 will be set to 100% and will remain there until such time as the roomtemperature increases to above the LOW temperature limit. This is toprovide heat to the microenvironment 44 on colds days where thetemperature of the farrowing room 40 never reaches the LOW temperaturelimit.

[0038] In the control algorithm embodied in the chart of FIG. 1, thepower setting of the power control 10 varies linearly over the controlband defined by the LOW and HIGH temperature limits by 5% for eachdegree of change in the room temperature. For a control device rated at120 volts, for each degree change, the power output of the power control10 will vary by 6 volts. Accordingly, on day 1 of operation and wherethe temperature of the farrowing room 40 is 85° F., the power outputsetting of the power control 10 will be 25% of rated power.

[0039] As the requirements of the piglets for supplementary heat duringtheir first weeks of life gradually diminish, the power output settingsof the power control 10 will be revised downward. In the embodimentshown in FIG. 1, the microenvironment 44 is heated for the first 25 daysof the piglets' lives, with the output of the power control 10 beinglowered each day. Note that this period may be varied from zero on upaccording to the needs of the particular application to which the powercontrol 10 is adapted. Note also that the time period over which thepower control 10 is used may be measured in any useful time measure,from seconds to years. The drop in the output of the power control 10over a period of time is in the embodiment of FIG. 1 determined bydropping the LOW and HIGH temperature limits by one degree Fahrenheiteach day over the selected 25-day period. This has the practical effectof lower the range of power outputs available to the power control 10 by5% per day over the given period.

[0040] It is to be understood however, that the power output of thepower control 10 may be modulated in a non-linear and/or discontinuousfashion over a given control band and over a selected period of time.Because the output of many heating devices 30 is not linear and may evenbe discontinuous with respect to the voltage applied thereto, modulatingthe power output of the power control 10 in a linear fashion will resultin non-linear or discontinuous output from the heating device 30. As itis desirable to provide at least a continuous heat output from theheating devices 30, the control algorithm whereby the power control 10modulates the power output therefrom may be adapted to provideelectrical power to the heating devices in a non-linear and/ordiscontinuous manner.

[0041] As can be seen in FIG. 8, heating devices 30 such as a heat lampwill, for a given applied voltage, yield a power output that isnon-linear with respect to the power (voltage) input to the heatingdevice 30. Note that the output of a typical heating device 30 is shownin the Figure as line 31 b. Accordingly, where it is desirable to ensurethat the output of the heating devices 30 be linear as shown by line 31a which represents an ideal linear power output, the voltage applied tothe heating devices 30 by the power control 10 will be variednon-linearly over the control band in order to drive a linear output forthe heating devices 30. It is to be understood that the function used tocalculate the percent power output of the power control 10 would bespecific to each heating device 30. Resistive heating devices 30 such asheat pads are more generally linear in their response and accordinglythe function used to calculate the power to be applied to a heat padwould be linear in nature. As heat lamps vary in their output as shownin FIG. 8, the function used to determine the output of the powercontrol 10 would more closely approximate a homolog of the curve shownin the Figure. Again, it is desirable to provide a continuous heatoutput from the heating devices 30 in order to increase the comfort andproductivity of the piglets. Accordingly, it is preferred to utilize analgorithm for determining the power output of the power control 10 thatresults in a continuous power output from the heating devices 30. Thepreferred continuity would apply to both the output of the heatingdevices 30 over the control band temperatures and over time. Note thatboth the control band HIGH/LOW temperature limits and the period overwhich the HIGH/LOW temperature limits are reduced may be preset for aparticular operation, in the present case a farrowing operation, or maybe modified directly by the user of the power control. In either case,the user may override the preset control band and the time period overwhich the power control is used, or the rate at which the control bandis modified by direct input of information into the power control 10.

[0042]FIG. 3 represents one embodiment of the circuitry of a powercontrol 10 of the present invention. The power control 10 comprises amicroprocessor 50. One suitable microprocessor 50 includes integratedmemory but may instead be coupled to a suitable RAM and/or ROM memorydevice. The microprocessor 50 is programmed with an object code thatmanages the overall operation of the power control 10, as describedabove.

[0043] The power control 10 implements a unique open loop process forproportionally controlling the power (voltage) applied to a plurality ofheating devices 30 based on the temperature of a larger environment andelapsed time or animal age for the purpose of achieving an optimizedthermal microenvironment. The power control is capable of operating inCelsius or Fahrenheit modes using a 50/60-Hertz power source.

[0044] A user interface 52 is built into the enclosure 12 and preferablyconsists of a 3-digit numeric display 54 and a number of pushbuttonswitches 56, preferably four, along with the related microprocessorinterface components including display driver transistors 60, diodes 62,resistor arrays 64 and the necessary electrical connectors that areconstructed and arranged as shown in FIG. 3. Note that the userinterface 52 may comprise any useful combination of input mechanisms anddisplay devices known to those skilled in the art. The user interface 52may be used to start the operation of the power control 10, set theappropriate time period over which the control band temperatures will bemodified, to input the control band temperatures or virtually any otherdatum needed to implement the algorithm set forth hereinabove. In someembodiments, the user interface 52 may be used to “lock” the powercontrol 10 in order to prevent accidental data entry, i.e. to preventaccidental entry of erroneous commands or data.

[0045] An internal temperature sensor 58 measures the temperature withinthe enclosure 12 and communicates its readings to the microprocessor 50.The object code with which the microprocessor 50 is programmed includesinstructions that will temporarily shutdown the power control 10 if theinternal temperature rises above approximately 150° F.-160° F. Note thatthe shutdown temperature is variable depending on the nature of thecomponents that make up the circuitry and the setting in which the powercontrol 10 is used.

[0046] The external temperature sensor 22 is electrically connected tothe microprocessor 50 through respective male and female coupling halves68 and 70, though the sensor 22 may be permanently connected as bysoldering. As indicated above, these coupling halves 68, 70 preferablymake up a liquid tight strain connectors 24. The sensor 22 measures theroom temperature and communicates its readings to the microprocessor 50.A nonvolatile memory chip 66 is electrically coupled to themicroprocessor 50 and is used to store various parameters and operatinginformation such as the temperature readings from the sensor 22. Thenonvolatile memory chip 66 also retains all power control operationalsettings in the event of a power failure.

[0047] The power supply 71 translates the nominal 120 VAC (or with readymodification 240 VAC) received through power cord 14 conductors 72 toapproximately 4.5 VDC for proper operation of the aforementioned lowvoltage circuitry. Resistors 74 couple the line voltage frequency intothe microprocessor 50 to provide a suitable synchronization signal, inthis case at 50/60 Hertz. Microprocessor 50 controls the power supply 71so as to apply power to the heating devices 30 in a gradual mannergenerally known as a “soft start”. The soft start application of voltageto the heating devices 30 prevents voltage surges from damaging theheating devices 30 by limiting the power applied to, for example, a heatlamp. Because heat lamps have a low resistance when they are cold andare first powered up, the application of full power to a cold lamp willresult in momentary high inrush currents that can damage the lamp.

[0048] A solid-state power switch known as a triac 76 directly controlsthe voltage applied to the heating devices 30 through conductors 73 andis itself controlled by signals received from transistor 78. Resistor 80and capacitor 82 form a snubber circuit, along with a varistor 84,protect the triac 76 from voltage surges. Filter coil 86 and capacitor88 form a low pass filter for minimizing generated electromagneticnoise.

[0049] Filter coil 86 in this embodiment, doubles as part of a faultdetection circuit that also includes switch 90. Switch 90 is a magneticswitch that is magnetically coupled to filter coil 86 such that theswitch 90 closes when a magnetic field produced by current flowingthrough the filter coil 86 reaches a predetermined strength that isassociated with a short circuit condition. The microprocessor 50periodically checks the open/close status of switch 90 to determine if ashort circuit condition has been detected. Upon detecting a closedswitch condition, the microprocessor 50 cuts power to the heatingdevices 30 for approximately 5 seconds and then slowly reapplies it. Ifthe short circuit condition remains, the power is again cut for 5seconds, and again slowly reapplied. In a preferred embodiment, thiscycle will repeat for as long as the short circuit condition exists.However, it is to be understood that switch 90 may also remain openuntil manually reset.

[0050] The snubber filter defined by resistor 80, capacitor 82 andvaristor 84, along with the low pass filter defined by filter coil 86and capacitor 88, prevent the triac 76 from being inadvertently openedduring power failures and brownouts or when the power control 10 issubjected to the presence of nearby electrical noise. The power control10 may also include software and/or additional circuit mechanisms thatprotect the triac 76 from voltage fluctuations and spikes.

[0051] Microprocessor 50 controls the power supply 71 so as to applypower to the heating devices 30 in a gradual manner generally known as a“soft start”. The soft start application of voltage to the heatingdevices 30 prevents voltage surges from damaging the heating devices 30and especially the bulbs of a heating lamp. A preferred embodiment ofthe present invention comprises a distributed power control system forcontrolling a plurality of heating devices 30 used to create amicroenvironment 44 within a larger environment as described above inconjunction with FIG. 4. See FIG. 5. Each of the microenvironments 44are heated by one or more heating devices 30. The heating devices 30pictured in FIG. 5 are heating lamps, though it is to be understood thatother heating devices such as heating mats, quartz radiant heaters, orstandard resistant wire electric heaters may be used as well. Theheating devices 30 are connected to one or more sources of electricalpower 100 by conductors 101 that are coupled to the heating devices 30in a hard connection or a removable plug as shown schematically at 103.The provision of electric power from the power source 100 to which eachof the heating devices 30 are connected is controlled by a number ofslave switches 102. Each of the slave switches 102 is in turnelectrically coupled to a master control 104 by a communications means108, which may be an electrically conductive cable, a wirelesstransmitter, or a communications cable such as a telephone cable orfiber optic cable. The master control 104 has an external temperaturesensor 106 attached thereto for sensing the temperature within thefarrowing room 40 in the same manner as temperature sensor 22 describedhereinabove. The temperature sensor 106 of the master control 104 istherefore constructed and arranged to sense the ambient temperaturewithin the farrowing room 40 and to provide this data to amicroprocessor (not shown) that directs the plurality of slave switches102 to allow a predetermined quantity of electrical power to flow fromthe power source 100 to the heating device 30.

[0052] The distributed power control 10 described above is illustratedschematically in FIG. 9. The master control 104 is connected to theslave switch 102 by a communications means that in this embodiment is aserial communication cable 108. The temperature sensor 106 isoperatively coupled to the microprocessor 150 of the master control 104.The microprocessor 150 also has a numeric display 152, a RAM and/or ROMmemory device 154, an input device 156 such as a keypad or the like, aninternal temperature sensor 158, and a power supply 160 that providesthe necessary power for controlling the microprocessor 150 and itsattached devices.

[0053]FIG. 9 also illustrates schematically the slave switch 102. Theslave switch 102 is typically distant to the master control 104 andtherefore includes its own microprocessor 162. The microprocessor 162 ofthe slave switch 102 is coupled to the master control 104 bycommunications means 108. The microprocessor 162 has coupled thereto anoutput device 164 such as a status LED or a numeric display, a RAMand/or ROM memory device 166, an input device 168 that allows for localcontrol of the slave switch 102, a fault control circuit 170, and apower supply 172. The power supply 172 receives power from a powersource 100 such as a breaker panel and provides the power to operate themicroprocessor 162 and its attendant devices and also provides power toa power control switch 174. The power control switch 174 is also coupledto and controlled by the microprocessor 162 and regulates power that isapplied to a heating device 30. The power control switch 174 alsoincludes an RCL filter for preventing electromagnetic interference. Theinductor of the RCL filter of the power control switch 174 ismagnetically coupled to the fault control circuit 170 such that wherethe magnetic field present in the inductor of the RCL filter exceeds apredetermined set point, the fault control circuit 170 will cut power tothe heating device 30 as the presence of large magnetic fields in theinductor of the RCL filter is indicative of a fault condition in thepower control 10. Note that magnetically coupling the inductor of theRCL filter to the fault control circuit 170 requires only a singleinductor in the power control switch 174.

[0054] The distributed embodiment of the power control 10 illustrated inFIGS. 5-7 operates in the same manner as does the embodiments describedin conjunction with FIGS. 2-4 above. However, the manner in which theslave switches 102 are arranged with respect to the master control 104may vary from application to application.

[0055] A preferred embodiment of the distributed power control 10involves providing a single power source 100 for a plurality ofmicroenvironments. The slave switch 102 is coupled between the singlepower source 100 and the heating devices 30 used to create the pluralityof microenvironments 44. Note that each microenvironment 44 may requiremore than one heating device. Accordingly, a single slave switch 102 maybe used to control multiple heating devices 30 in multiplemicroenvironments 44. Because of the distributed nature of theembodiment of the power control 10 illustrated in FIGS. 5-7, a singlemaster control 104 may control the microenvironments 44 for a largenumber of farrowing sows at a given time. Note that where a singlemaster control 104 is used, it may be necessary to ensure that farrowingsows are brought into estrus and inseminated on an identical schedule soas to ensure that the resulting piglets are all of substantially thesame age.

[0056] Another embodiment of the distributed power control 10 involvesproviding a single slave switch 102 for each microenvironment andcoupling the slave switches 102 to the master control 104 usingcommunication means 108. In this embodiment, the slave switches 102 manybe operated identically by the master control 104 or may be operatedindependent of one another such that each microenvironment 44 in afarrowing room 40 might have a different temperature at a given time. Inthese cases, it is preferable to provide a master control 104 thatcomprises a programmable logic controller (PLC) or, more preferably, aremotely located personal computer or other computing device having aprocessing power sufficient to track independently each of the farrowingrooms 40, farrowing crates 42, and microenvironments 44 associatedtherewith. With this embodiment of the distributed power control 10, forexample, a sow two weeks out of cycle with the remainder of theimpregnated sows may be accommodated without undue effort. By using adistributed system of this type a single computer/master control 104could be used to control hundreds or even thousands of microenvironments44 all on different schedules without regard to the development rate ofthe piglets involved.

[0057] In operation, the master control 104 utilizes the temperaturesensor 106 to sense the ambient temperature within the farrowing room40. The master control 104 then checks to see where the sensedtemperature falls with respect to a specified control band as describedhereinabove. A microprocessor within master control 104 then selects anappropriate power setting that is transmitted from the master control104 to the slave switches 102. The slave switches 102 then adjust thepower flowing from the source 100 to the heating devices 30. The slaveswitches 102 comprise a power supply that receives power from powersource 100 and a switching mechanism that may include a triac asdescribed hereinabove in conjunction with FIG. 3. Another embodiment ofthe switching mechanism may comprise a pair of thyristors and anassociated circuit that controls them. The switching mechanism iscoupled to the master control 104 via communications means 108 andreceives instructions therefore regarding the amount of power that is tobe applied to the heating devices 30. In addition, it is desirable toprovide the slave switches 102 with the fault detection and filtermechanisms described in conjunction with FIG. 3 above to ensure the safeand reliable operation of the distributed power control 10.

[0058] The foregoing is considered as illustrative only of theprinciples of the invention. Furthermore, since numerous modificationsand changes will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described. While the preferred embodiment has been described,the details may be changed without departing from the invention, whichis defined by the claims.

What is claimed is:
 1. A method of improving animal health, well-being, and growth comprising the steps of: providing a heating device constructed and arranged to create a heated microenvironment within a larger environment; selecting a low temperature limit at and below which the heating device will caused to operate at substantially 100% of its rated power; selecting a high temperature limit at which the heating device will be caused to operate at substantially 0% of its rated power; measuring a temperature of the larger environment outside of the microenvironment; and applying power to the heating device where the temperature of the larger environment is below the high temperature limit such that the heating devices creates the heated microenvironment, the power applied to the heating device being varied with the temperature of the larger environment so as to maintain a continuous heat output from the heating device.
 2. The method of claim 1 wherein the power applied to the heating device varies linearly between 0%-100% of the heating device's rated power over the range defined by the high and low temperature limits.
 3. The method of claim 1 wherein the power applied to the heating device is varied between 0%-100% of the heating device's rated power over the range defined by the high and low temperature limits such that the output of the heating device varies linearly over the range defined by the upper and lower temperature limits.
 4. The method of claim 1 wherein the power to the heating device is cut off when the temperature of the larger environment is above the high temperature limit.
 5. The method of claim 1 wherein the power to the heating device is set to 100% of rated power when the temperature of the larger environment is below the lower temperature limit.
 6. The method of claim 1 wherein the high and low temperature limits are periodically lowered over a predetermined period of time.
 7. The method of claim 1 wherein the high and low temperature limits are varied in one of a linear or non-linear manner.
 8. The method of claim 1 wherein the high and low temperature limits are lowered continuously over a predetermined period of time.
 9. The method of claim 8 wherein the high and low temperature limits are varied in one of a linear and non-linear manner.
 10. A power control mechanism for controlling the power applied to a heating device so as to create a heated microenvironment within a larger environment, the mechanism comprising: a data processor operatively coupled to a memory device and to an operator control input/output device; a temperature sensor for sensing a temperature of the larger environment, the temperature sensor being operatively coupled to the data processor; and, a power input coupled to a variable power switch that is in turn coupled to a power output, the variable power switch being also coupled to and controlled by the data processor according to the temperature sensed by the temperature sensor, the power output being coupled to a heating device whose output creates a heated microenvironment within the larger environment.
 11. The power control mechanism of claim 10 further comprising a fault checking circuit coupled to the microprocessor, the microprocessor being programmed to open the variable power switch if a fault condition is sensed.
 12. The power control mechanism of claim 11 wherein a low pass filter and the fault checking circuit are coupled by an induction coil that forms an operative part of the low pass filter and the fault checking circuit.
 13. The power control mechanism of claim 11 wherein the memory device has a power control algorithm recorded thereon, the power control algorithm acting to set a high temperature limit, above which power to the heating device is cut off, a low temperature limit at and below which power applied to the heating device is set to 100% of the rated power of the heating device, the power control algorithm varying the power applied to the heating device based on the output of the temperature sensor so as to vary the heat output of the heating device continuously.
 14. The power control mechanism of claim 10 wherein the variable power switch comprises a switching mechanism chosen from a group consisting of a rheostat, a triac, and one or more thyristors.
 15. The power control mechanism of claim 14 wherein the variable power switch is controlled by the data processor to provide power at levels between 0-100% of the rated power of its heating device for temperatures in the larger environment defined by the high and low temperature limits, the power control algorithm being constructed and arranged to supply power through the variable power switch such that a heat output of the heating device is linear over an operational range that is defined by the upper and lower temperature limits.
 16. The power control mechanism of claim 10 wherein the data processor, memory device, operator control input/output and temperature sensor are positioned outside of the microenvironment and remotely from the variable power switch.
 17. The power control mechanism of claim 16 wherein the data processor is coupled to a plurality of variable power switches, each of the plurality of variable power switches being constructed and arranged to control power output to at least one heating device positioned within a microenvironment.
 18. The power control mechanism of claim 16 wherein each of the plurality of variable power switches controls a heating device located in a respective microenvironment.
 19. A power control for heating devices used to create a heated microenvironment for animals, the power control device comprising: a sealed enclosure; a power input cord for supplying power to the interior of the sealed enclosure; a power output cord for supplying power from the sealed enclosure to at least one heating device; a temperature sensor constructed and arranged to sense an ambient temperature outside the sealed enclosure and to transmit signals related to the sensed ambient temperature into the sealed enclosure; and, a power control circuit comprising: a microprocessor; a non-volatile memory mechanism operatively connected to the microprocessor; a display means connected to the microprocessor for displaying information concerning the operation of the power control exterior to the sealed enclosure; an input means coupled to the microprocessor whereby a user of the power control device may input information to the microprocessor to modify the operation of the power control device; and, a power control circuit comprising at least one triac switch, the triac switch being coupled between a power source and the at least one heating device, the triac switch being controlled by the microprocessor to meter the power output from the power control to the heating device.
 20. A power control for metering the power transmitted to a heating device having a rated power capacity that is constructed and arranged to create a warm microenvironment conducive to the health and growth of an animal, the percentage of the rated power capacity applied to the heating device being related to an ambient room temperature and the age of the animal.
 21. The power control of claim 20 wherein the power control device sets an high temperature limit that is periodically lowered over a predetermined time period.
 22. The power control device of claim 21 wherein the high temperature limit declines by one degree per day for 25 days.
 23. The power control device of claim 21 wherein the power control sets a high and a low limit, the high and low limits being related to an ambient temperature outside of the microenvironment, the power control transmitting proportionately more power to the heating device where the ambient temperature is nearer the low limit and proportionately less power where the ambient temperature is nearer the high limit. 